Current issues of ACP Journal Club are published in Annals of Internal Medicine


Therapeutics

Oat bran and oatmeal for 6 weeks reduced total and LDL cholesterol in adults with hypercholesterolemia

ACP J Club. 1991 Jul-Aug;115:20. doi:10.7326/ACPJC-1991-115-1-020


Source Citation

Davidson MH, Dugan LD, Burns JH, et al. The hypocholesterolemic effects of β-glucan in oatmeal and oat bran. A dose-controlled study. JAMA. 1991 Apr 10;265:1833-9.


Abstract

Objective

To examine the dose-response relationship between the water-soluble fiber (β-glucan) content of oatmeal and oat bran and serum cholesterol levels in adults with hypercholesterolemia on a low-fat, low-cholesterol diet.

Design

Randomized, parallel, controlled trial with 7 comparison groups. An 8-week dietary-compliance period preceded a 6-week fiber trial followed by a 6-week washout period.

Setting

Urban medical center in the United States.

Participants

211 volunteers, aged 30 to 65 years. They were not pregnant, lactating, or more than 50% overweight, and had no serious metabolic disorders.

Intervention

156 participants with low-density lipoprotein cholesterol (LDL-C) levels of > 4.14 mmol/L or between 3.37 and 4.14 mmol/L with multiple risk factors, despite dietary compliance, were randomized to 1 of 7 daily, dry-cereal supplements: 3 with oatmeal (OM) (28 g, 56 g, and 84 g), 3 with oat bran (OB) (28 g, 56 g, and 84 g), and a placebo group (28 g farina). The β-glucan content of supplements, per 28 g, was 0 g (farina), 1.2 g (oatmeal), and 2.0 g (oat bran). Participants continued on the low-fat diet through the 6-week washout period.

Main outcome measures

Total cholesterol, LDL-C, high-density lipoprotein cholesterol (HDL-C), and triglyceride levels.

Main results

140 participants (90%) were > 80% compliant and were included in the analysis. At the end of the fiber-supplement period (week 6), mean decreases in total cholesterol levels in comparison with the placebo group had occurred for the 3 groups with the highest daily intake of β-glucan, OM-84, OB-56, and OB-84 (P = 0.02, 0.003, and 0.03, respectively). LDL-C level differences from placebo were found for OM-84 (P = 0.02), OB-56 (P < 0.001), and OB-84 (P = 0.02), with mean decreases of 10%, 16%, and 12%, respectively. A linear relationship (r of the means = 0.81) was observed between change in LDL-C leveland daily β-glucan intake. No significant differences from placebo were found for HDL-C or triglyceride levels. At the end of the 6-week washout period, total cholesterol and LDL-C levels tended to return to baseline levels.

Conclusion

56 g of oat bran or 84 g of oatmeal per day for 6 weeks reduced total cholesterol and low-density lipoprotein cholesterol levels in compliant adults with hypercholesterolemia on a low-fat diet.

Source of funding: Quaker Oats Company.

Address for article reprint: Dr. M.H. Davidson, Chicago Center for Clinical Research, 800 South Wells, Suite M-25, Chicago, IL 60607, USA.


Commentary

This study attempts to define the hypocholesterolemic dose-response for oatmeal and oat bran for patients following a National Cholesterol Education Program (NCEP) step 1 diet. The 7 study groups were small, which limited the power of the study to detect small differences.

The study confirms the findings of others, that soluble fiber in the form of oat bran or oatmeal lowers total cholesterol and LDL-C levels without an adverse effect on HDL-C levels. It also suggests that 56 g of oat bran is as effective as 84 g of oat bran or oatmeal in reducing total cholesterol and LDL-C levels. A recent study of similar patients with a larger sample size found that 56 g of instant oatmeal for 8 weeks led to a 4.8% and 5.4% decrease in total cholesterol and LDL-C levels, respectively (1), suggesting that lower doses may still have a beneficial effect. Oat bran may be more effective than wheat or rice bran because of its higher content of water-soluble fiber, β-glucan. Its mechanism of action is uncertain, although the respective capacities of soluble fiber to bind bile acids and interfere with fat absorption, to increase bile-acid excretion, and to be fermented to short-chain fatty acids and thus to suppress hepatic cholesterol synthesis, have all been proposed.

From the clinician's perspective, recommending a significant increase in dietary oat bran or oatmeal seems justified and may increase the effectiveness of the NCEP step 1 diet by another 5% to 15%. However, beware: Adding whole milk to oatmeal may lessen the benefit and not all "oat bran" muffins are low in fat and cholesterol—or even have much oat bran!

David L. Bronson, MD
The University of VermontBurlington, Vermont, USA


Reference

1. Van Horn L, Moag-Stahlberg A, Liu K, et al. Effects on serum lipids of adding instant oats to a usual American diet. Am J Public Health. 1991;81:183-8.